JPS6256750B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylindrical linear motor that is generally used, for example, in an automatic door opening/closing drive device.

Conventionally, this type of linear motor generally consists of a coil built into the stator and a rod (iron core) that slides through the center of the coil, and the direction of the excitation current is reversed by switching a switch attached to the stator. Alternatively, the stator is configured to reciprocate (for example, JP-A-49-125804 and JP-A-50-106114). In the case of an electromagnetic pump, for example, as disclosed in Japanese Patent Application Laid-Open No. 51-28606, the rod is formed into a hollow pipe-shaped piston with a valve at one end, and the reciprocating motion of the piston excited by a coil is Therefore, there are those in which the fluid is transferred linearly from one side of the cylinder to the other, as in, for example, Japanese Patent Application Laid-Open No. 53-34106,
Some systems generate a rotating magnetic field in a large number of coils arranged in a circle and rotate a valve installed in the iron core to transfer the liquid in the duct to one side, but in either case, the magnetic field creates a rotating magnetic field. The secondary conductor that operated in this case was a rod, that is, a solid material.

A conventional actuator (linear motor) with a solid iron core inserted into the coil as described above,
The same applies to the case where the magnetic field remains stationary without any movement until the strength of the magnetic field is balanced with the frictional resistance based on the mass of the iron core, and once equilibrium is exceeded, it moves rapidly and stops at the end of the stroke. Stop suddenly (see solid line in Figure 4).
However, when using a cylindrical linear motor, it has been desired to improve its operation so that it can be smoothly controlled, such as in an air cylinder or a hydraulic device.

Therefore, the present invention fixes a partition by forming a small gap around the center of the cylinder that allows liquid metal to flow along the axial direction, and a plunger is installed in each cylinder divided into two by this partition. is loaded to form a pair of left and right cylinder chambers that communicate with each other through the small gap between both sides of the partition wall and the plunger, and a piston rod that penetrates the partition wall and is slidably provided to the left and right, While the plungers are fixed together and the liquid metal is filled in the cylinder chamber and the small gap, a stator is fixed on the outside of the cylinder which corresponds to the outside of the small gap, and the stator is placed in the small gap in the stator. The present invention provides a cylindrical linear motor characterized in that coils are provided close to each other.

Since the linear motor of the present invention is constructed as described above, when a current is passed through the coil to form a magnetic field, the liquid metal in the small gap becomes a secondary conductor and is excited, following the direction of the magnetic force at that time. The liquid metal moves from one cylinder chamber to the other through the small gap. Therefore, a reduced pressure is created in one cylinder chamber and a pressurization in the other cylinder chamber, causing the thrust of the liquid metal in the small gap to the piston rod via the respective plunger to reduce the cross-sectional area between the small gap and the cylinder chamber. The thrust multiplied by the ratio of is given.

As mentioned above, the present invention enables linear motors to operate in the same way as fluid pressure devices such as air cylinders by replacing the secondary conductor of the solenoid, which was conventionally a fixed iron core, with a fluid called liquid metal. Accordingly, the above-mentioned conventional drawbacks can be eliminated.

Embodiments of the present invention will be described below with reference to the drawings.

In the figure, 1 is a cylindrical cylinder. 3 is a partition wall that is fixed in the center of the cylinder 1 and divides the cylinder 1 into left and right halves. A small gap 2 is formed between the periphery of the partition wall 3 and the inner surface of the cylinder 1 so that liquid metal, which will be described later, can flow in the axial direction of the cylinder 1. Reference numerals 4 and 4' denote a pair of left and right cylinder chambers formed within the cylinder 1 by the partition wall 3.
Plungers 6 and 6' are movably mounted in the cylinder chambers 4 and 4', respectively. 7 is a liquid metal filled in the cylinder chambers 4, 4' and the small gap 2 formed between both sides of the partition wall 3 and the plungers 6, 6'. 8 is a stator fixed to the outer periphery of the cylinder 1 on the outside of the small gap 2. A pair of left and right coils 9 and 9' are provided in the stator 8 close to the small gap 2. 10 is a switch that alternately switches the current flowing through the coils 9, 9'. In this example,
In order to bring the coils 9, 9' in the stator 8 as close as possible to the liquid metal 7 in the small gap 2, the cylinder 1 is divided into left and right halves as shown in FIG. A cylindrical thin-walled pipe 1 that is integrally fixed to the stator 8 and forms the inner periphery of the stator 8.
By fixing both ends of the cylinder 1 to the inner end surface of the bisected cylinder 1, it is formed into a continuous integral body as schematically shown in FIG. Further, the partition wall 3 is provided with ribs 12 arranged between the inner surface of the thin-walled pipe 11 and the outer circumferential surface of the partition wall 3 as shown in FIGS. It is fixed within the cylinder 1 with a small gap 2 formed therein. Further, as the liquid metal 7, a mixture of conductive metal powder such as aluminum powder and copper powder is used.

Next, the operation of this embodiment will be described.

When current is applied to one of the coils 9 through the switch 10, the liquid metal 7 in the small gap 2 becomes a secondary conductor due to the magnetic field generated in the coil 9, and moves in accordance with the direction of the magnetic force. This movement of the liquid metal 7 causes a reduced pressure in one cylinder chamber 4 as the liquid metal 7 flows out, and increases pressure in the other cylinder chamber 4' as the liquid metal 7 flows in. Both cylinder chambers 4,
The pressurization and negative pressure 4' cause the plungers 6, 6' to move in the direction of the flow of the liquid metal 7, and the force can be taken out of the system as a thrust force of the piston rod 5. Moreover, if the switch 10 is switched, the piston rod 5 moves in the opposite direction.

The speed of movement of the piston rod 5 is reduced to a speed equal to the speed of movement of the liquid metal 7 in the small gap 2 multiplied by the ratio of the cross-sectional areas of the small gap 2 and the cylinder chambers 4, 4'.

As described above, the present invention fixes the partition wall 3 in the center of the cylinder 1 by forming the small gap 2 around which the liquid metal 7 can flow, and the plungers 6 and 6 are respectively placed in the cylinder divided into two by the partition wall 3. 6' is loaded to form a pair of left and right cylinder chambers 4, 4' which communicate with each other through the small gap 2, and the plungers 6, 6' are respectively inserted into the piston rod 5 which slidably penetrates the partition wall 3. At the same time, the cylinder chambers 4, 4' and the small gap 2 are filled with liquid metal 7, the stator 8 is fixed to the outer periphery of the cylinder 1 on the outside of the small gap 2, and the small gap is formed inside the stator 8. 2
Coils 9 and 9' are provided so as to be close to the small gap 2, and the liquid metal 7 in the small gap 2 is excited as a secondary conductor. , the pair of left and right cylinder chambers 4,
Pressure and negative pressure are generated at the plunger 6,
6' in the direction of the flow of the liquid metal 7, thereby acting to impart a thrust to the piston rod 5.

According to the present invention, in which a fluid called liquid metal is used as a movable body driven by the magnetic force of a solenoid as described above, excitation also causes movement of the fluid, so the operation is similar to that of an air cylinder or hydraulic device. The vehicle starts and stops slowly in the same manner as the motion, and the rise and fall as shown by the broken lines in FIG. 4 are obtained. Therefore, it starts and stops smoothly, avoiding the sudden start and stop of conventional products that use a solid iron core as a movable body, and is slower than conventional products with the same diameter, but with less force. The amount of deceleration increases. On the other hand, unlike conventional fluid pressure devices, which require a separate drive source such as a motor or compressor, and the need for piping, fluid pressure devices that can be used in the same way can be made with an extremely simple power supply and wiring. It has the advantage of being usable in equipment, and is particularly suitable for driving devices for robots such as magic hands.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention. Second
The figure is a longitudinal sectional view taken along the line AA in FIG. 1. FIG. 3 is a block diagram schematically showing the entire embodiment. FIG. 4 is a chart showing the operation of the linear motor of the conventional product and the present invention. 1... Cylinder, 2... Small gap, 3... Partition wall, 4, 4'... Cylinder chamber, 5... Piston rod, 6, 6'... Plunger, 7... Liquid metal, 8... Stator, 9,9'...Coil, 10
...Switch, 11...Thin-walled pipe, 12...Rib.

Claims (1)

[Claims] 1. A small gap 2 is formed around the center of the cylinder 1 to allow liquid metal 7 to flow along the axial direction, and a partition wall 3 is fixed. A pair of left and right cylinder chambers 4, 4' are formed between both sides of the partition wall 3 and the plungers 6, 6' by loading the plungers 6, 6', respectively, and communicating with each other through the small gap 2. A pair of plungers 6 and 6' are respectively fixed to a piston rod 5 which is provided so as to be slidable left and right through the cylinder chambers 4 and 4.
4' and the small gap 2 are filled with liquid metal 7, while a stator 8 is fixed to the outer circumference of the cylinder 1 on the outside of the small gap 2, and a coil 9, A cylindrical linear motor characterized by being provided with 9'.